This device takes up very little space. It is just about exactly the size of a paperback book (of about the 500-page range), and very light at 369gr. (13oz) The dimensions are 6" X 3.5" X 2" It will fit in one of the side pockets of my Nirvana Rodeo harness.

It comes in an orange, polyester, Velcro-sided storage pouch. The "breakaway" sides allow the inflating device to pop open when immersed in water. The case has elastic loop, that allowed me to add a nylon belt, (not included) I can wear it around my waist, or with the belt looped over my neck. It could also be rigged to be permanently attached to the comfort bars of a paramoter.

NOTE: It is not US Coast
guard approved because of its limited buoyancy. On the plus side, the thing is light, compact, and better than nothing.

$139.00 from Stearns

$50-$89 bucks on eBay.(I e-stalked them on eBay and managed to pick one up for $39)

MUSTANG SURVIVAL - RESCUE STICK

Incredibly easy to use, the Rescue Stick™ provides rapid
flotation assistance to a person at risk of drowning. Simply remove the baton
shaped Rescue Stick™ from its waterproof bag and throw near the person. Once
contact is made with the water it inflates in seconds to a large horseshoe
shape keeping the victim afloat and their head above the water until help
arrives.

Measuring only 14" in length and weighing 15.5oz, the
Rescue Stick™ is the most versatile rescue flotation device available. Easily
stowed in a boat, vehicle, backpack or by the pool it will be accessible when
and where you need it.

The Rescue Stick™ is an invaluable tool for police officers
arriving first on scene to provide emergency flotation when no water rescue
gear is available. During a swift water rescue, fire departments can throw the
Rescue Stick™ to the victim to keep them afloat while a rescue plan is put into
action. Lifeguards can easily throw the Rescue Stick™ to someone in trouble to
keep their head above water until rescued. Recreational boaters can throw the
Rescue Stick™ to a man overboard while maneuvering to get them out of the
water.

•Can be thrown accurately 100 feet or further

•Automatically inflates in seconds when immersed in water
providing rapid emergency flotation

•Offers 35lb of buoyancy - twice the flotation of a typical
life jacket

Easy to repack and reuse - insert a new bobbin and screw in the
replacement handle containing

SIDE BY SIDE
If you or your organization is serious about SAR, I'd go with the Rescue Stick. It's bulkier, and more expensive, (and also more expensive to rearm) but the additional buoyancy could make a significant difference. The Stearns unit is tiny and compact, however, and quite a bit cheaper in price, and would be easier to keep more or less permanently attached to your motor. And as I said, it's better than nothing.
If you fly around water and beaches long enough, it seems to me that sooner or later a throwable flotation devi